The aims of this research are: 1) To investigate by gel electrophoresis a number of genetic loci in populations of several closely related species of Drosophila. We wish to determine what fraction of the genome displays genetic variability between populations of the same and different rank, the amount of genetic difference between populations, species, phylads and so on, and to relate this information to the evolutionary history of the group in such a way as to document the changes undergone by gene pools during speciation, during ecological shifts, during intercontinental colonizing episodes, and so on. Among other things, this provides us with direct evidence as to differential rates of evolution for different loci, for different loci in different lineages, themselves. In addition we are extending our investigations to detect and evaluate further genetic variability as this is evidenced by the application of additional criteria such as heat stability or pH sensitivity. In special cases enzymes will be characterized in greater detail through investigation of reaction kinetics. 2) To investigate, by making the complete set of reciprocal comparisons, the DNA hybridization relationships within the same group of species studies for enzyme evolution. This will permit us to compare rates of evolution as these are evidenced by different types of comparisons (DNA change vs allele frequency change) and to compare "phylogenies" derived from DNA with those derived cytologically and those derived from genetic distances calculated from enzyme data.